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-   -   Do patched up inner tubes slow you down? (https://www.bikeforums.net/showthread.php?t=1196088)

DeathCurse7 03-19-20 12:22 PM

Do patched up inner tubes slow you down?
 
So i wanted to save some money and just repair inner tubes with a patch kit. I was wondering if this would increase my rolling resistance?

indyfabz 03-19-20 12:26 PM

Nothing slows me down except myself.

79pmooney 03-19-20 12:35 PM

Probably if you can find equipment accurate enough and can eliminate every other factor. (Most people would call this obsessive.)

Real life - I've patched many tubes many times and the only time I notice the patches is when I pull the tube out. My norm at tube replacement is 5 patches. Now, 5 patches does add some weight but not a lot. A small REMA patch kit weighs maybe an half an ounce. That (edit) half ounce includes 6 patches, one of which is large, a tube, a casing patch and sandpaper. The box itself weighs probably 1/'3 the total. If my guesses are close, the rest weighs 10g. So maybe 5 grams for 5 patches and glue used. On a 70 gram tire. ON a 1000g wheel. On a 7000g bike. Ridden by a 70,000g rider. I would expect the additional rolling resistance to play out about the same.

ridelikeaturtle 03-19-20 12:46 PM

Unless you patch them incorrectly and they lose air... no.

bbbean 03-19-20 12:55 PM


Originally Posted by DeathCurse7 (Post 21374257)
So i wanted to save some money and just repair inner tubes with a patch kit. I was wondering if this would increase my rolling resistance?

Yes. Does it make a difference? Depends. If you're a contender for the hour record or time trialling at the Olympics, the fraction of a watt difference could be an issue. For ordinary mortals, however (including most of us who race), the difference isn't enough to measure.

Personally, my race day wheelset is either tubular or tubeless. When I was racing on tubes, my race day wheelset had an unpatched latex tube. But I wouldn't (and haven't) hesitate(d) to use my backup wheelset with a patched tube in a race, and will train on patched tubes all day long.

delbiker1 03-19-20 12:57 PM

Only if the patch fails and you have to do it again.

Ghazmh 03-19-20 07:06 PM

Won’t the wheel be out of balance?

Sy Reene 03-19-20 07:09 PM

Patched tubes are faster than no tubes (unless you have tubeless tires, then it's a moot point).

RChung 03-19-20 10:25 PM


Originally Posted by DeathCurse7 (Post 21374257)
So i wanted to save some money and just repair inner tubes with a patch kit. I was wondering if this would increase my rolling resistance?

I've been wondering this for a while. I asked Josh Poertner on his Marginal Gains podcast about it: he thought it would but he hadn't tested it either. OTOH, Tom Anhalt thinks it won't. If you know these two guys you'll recognize that they rarely disagree, so I'll take it that the question is currently unresolved. I'll probably test it at some point but I haven't yet had a chance.

ridelikeaturtle 03-20-20 04:56 AM

Seriously, if anyone can successfully measure a statistically significant difference, *and replicate it*, then that research should be published. You'll win an Ig Nobel prize.

Sy Reene 03-20-20 06:32 AM

The real question is.. does a patched tube use less additional watts than carrying the additional weight of a spare fresh tube in your back pocket or saddlebag?

asgelle 03-20-20 07:16 PM


Originally Posted by RChung (Post 21374914)
I've been wondering this for a while. I asked Josh Poertner on his Marginal Gains podcast about it: he thought it would but he hadn't tested it either. OTOH, Tom Anhalt thinks it won't. If you know these two guys you'll recognize that they rarely disagree, so I'll take it that the question is currently unresolved. I'll probably test it at some point but I haven't yet had a chance.

I don’t see how adding a patch can not increase rolling resistance. After all, we know thicker butyl tubes result in higher RR than thinner ones. What is a patch other than a localized thickening of the tube? Now what the magnitude of that increase is and how difficult it would be to detect is another matter; but I don’t see how there could be any doubt about the direction of the change.

But giving Tom and Josh their due respect, I would be hesitant to rely solely on what is essentially a hand waving argument by analogy.

woodcraft 03-20-20 07:50 PM

Huh.

So if the patch is about .75" it would be about 1/112 of the wheel circumference and about 1/4 of the tube circumference.

The thickness of a patch is similar to the difference in thickness between a standard tube, and a lighter tube.

The difference in rolling resistance between those tubes is about 1 watt for pair of tires at 45kph,

so a patch could theoretically require about .0022 watts at 45kph.

https://www.aero-coach.co.uk/inner-t...ing-resistance


Then, if I have the math right, they suggest a 4 second difference in a 40k TT for 1 watt of RR,

so a tube patch could cost you .0088 of a second over a 40k time trial at 45kph.

ChrisAlbertson 03-20-20 09:12 PM

This is what I call the "standing on a sheet of paper argument". In theory if you are taller you can see farther. So does standing on a sheet of paper enable you to see farther?

There are many things like this that in theory should matter but the effect is so small as to be impossible to measure.

woodcraft 03-20-20 09:13 PM


Originally Posted by ChrisAlbertson (Post 21376422)
This is what I call the "standing on a sheet of paper argument". In theory if you are taller you can see farther. So does standing on a sheet of paper enable you to see farther?

There are many things like this that in theory should matter but the effect is so small as to be impossible to measure.




Sez you!

tomato coupe 03-20-20 09:23 PM


Originally Posted by ChrisAlbertson (Post 21376422)
This is what I call the "standing on a sheet of paper argument". In theory if you are taller you can see farther. So does standing on a sheet of paper enable you to see farther?

It depends. What color is the paper?

FeltF2Tarmac 03-20-20 10:19 PM

Red, so you can see further faster.

Kabuki12 03-21-20 01:42 AM

I have quite a few bikes in my stable that are rotated frequently. I can’t remember which ones have patched tubes so I really don’t know. Each bike has a seat pack or handlebar bag with a spare tube and a patch kit. I always end up patching over replacing the tube . I am not a racer so I really don’t care about speed as much as comfort and feel of the bike itself. I have noticed a difference in tires for sure ,but tubes?

Camilo 03-21-20 02:07 AM


Originally Posted by woodcraft (Post 21376333)
Huh.

So if the patch is about .75" it would be about 1/112 of the wheel circumference and about 1/4 of the tube circumference.

The thickness of a patch is similar to the difference in thickness between a standard tube, and a lighter tube.

The difference in rolling resistance between those tubes is about 1 watt for pair of tires at 45kph,

so a patch could theoretically require about .0022 watts at 45kph.

https://www.aero-coach.co.uk/inner-t...ing-resistance


Then, if I have the math right, they suggest a 4 second difference in a 40k TT for 1 watt of RR,

so a tube patch could cost you .0088 of a second over a 40k time trial at 45kph.

Could you re-do the calculation for 60kph, because we ride fast.

bruce19 03-21-20 06:10 AM

No. I'm running Mavic USTs.

woodcraft 03-21-20 11:33 AM


Originally Posted by Camilo (Post 21376577)
Could you re-do the calculation for 60kph, because we ride fast.



I'm not falling for that.

Nobody who rides that fast patches tubes.

Digger Goreman 03-21-20 11:40 AM

If patched tubes slowed me down, I would soon be cycling in reverse! :p

biker128pedal 03-21-20 07:33 PM

I bought smaller patches so they won’t slow me down. :D

eduskator 03-23-20 10:33 AM

They say there's no such thing as a stupid question, but what a stupid question...

woodcraft 03-23-20 10:44 AM


Originally Posted by eduskator (Post 21379842)
They say there's no such thing as a stupid question, but what a stupid question...



Seems like only yesterday that "Could I go faster with bigger tires?" was considered a stupid question...


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